Abstract : Ochlerotatus caspius and Oc. detritus, two major mosquito species considered as pests in Tunisia, are subjected to intensive insecticide treatments. Considering the large areas colonized by immature stages and high adult densities generated at each egg hatching period, the efficiency of insecticide control is limited. In order to define more suitable control strategies, we aim in this study to characterize the ecological niche of each mosquito species using multivariate analyses (CA, HAC). Our results show that larval densities of both mosquito species are mainly related to plant composition and salinity of breeding sites. Indeed, Oc. detritus is more adapted to salty biotopes mainly colonized by Sarcocornia fruticosa when Oc. caspius is mostly associated to biotopes with more diversified vegetation bearing a low salinity and predominantly occupied by Juncus maritimus.